1. Technical Field
Various embodiments relate generally to a semiconductor memory device and, more particularly, to a semiconductor memory device including memory cells stacked in a direction perpendicular to a substrate.
2. Related Art
In order to increase data storage capacity, more memory cells are formed within a defined area. To make room for additional memory cells, size of memory cells have decreased. However, there are limitations in reducing the size of memory cells. Another method has been proposed, which provides a three-dimensional (3D) structured memory block (or memory string) where memory cells are stacked in a direction perpendicular to a surface of a semiconductor substrate. This 3D structured memory string may include a vertical channel formed of silicon. The vertical channel may be formed between a bit line and a common source line.
Recently, a method of forming even more 3D structured memory blocks within the defined area has been in demand, and a method of preventing deterioration of electrical characteristics caused thereby is also being sought.